Methods of determining the optimal erase and write power, and recording apparatus with devices for said methods
AssigneeKoninklijke Philips Electronics N.V.
InventorsGuo-Fu Zhou, Roel Van Woudenberg, Johannes H. M. Spruit
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Abstract
The application relates to methods and devices for determining the optimal erase (17) and write powers for erasing and writing information on an optical record carrier (85). These optimal powers are determined from two powers, Pmin (15) and Pmax (16), found at specific points, (22) and (24), in a curve (10) where the normalized reflected power (12) is plotted versus the test power (11).
Claims20
A method of determining an optical modifying power for modifying the reflection of an area of a record carrier of the type in which marks are written by locally heating the record carrier with radiation pulses having a power higher than a minimum writing power sufficient to reduce the reflection of the radiation pulses, and the marks are erased by locally heating the record carrier at the marks with radiation pulses having a power, lower than the minimum writing power but higher than a minimum erase power which increases the reflection of radiation with respect to the marks, the method comprising the steps of:
- writing test marks on the record carrier by locally heating the record carrier with radiation pulses having a power higher than the minimum writing power;
- determining a minimum erase power (Pmin) of the radiation pulses, at which the optical properties of the record carrier at the test marks do not substantially change when the record carrier is irradiated at a power which is lower than the minimum erase power, and the optical properties of the record carrier at the test marks change to such an extent that the normalized reflected power increases, when the record carrier is irradiated at a power which is higher than the minimum erase power;
- determining a maximum erase power (Pmax) of the radiation pulses, at which the optical properties of the record carrier at the test marks change when the record carrier is irradiated at the maximum erase power at the test marks, such that the normalized reflected power becomes maximal;
- determining the optimal modifying power (PM) from the equation P M = χ · ( P min + P max ) α
- in which α is a constant known in advance and χ is a variable which is dependent on properties of the record carrier.
A recorder for writing marks by locally heating a record carrier with radiation pulses having a power higher than a minimum writing power sufficient to reduce the reflection of the radiation pulses from the record carrier, and for erasing the marks by locally heating the record carrier at the marks with radiation pulses having a power, lower than the minimum writing power but higher than a minimum erase power, sufficient to increase the reflection of radiation from the record carrier at the marks, the recorder comprising:
- means for determining a minimum erase power (Pmin) of the radiation pulses, at which the optical properties of the record carrier at test marks written on the record carrier do not substantially change when the record carrier is irradiated at a power which is lower than the minimum erase power, and the optical properties of the record carrier at the test marks change to such an extent that the normalized reflected power increases, when the record carrier is irradiated at a power which is higher than the minimum erase power;
- means for determining a maximum erase power (Pmax) of the radiation pulses, at which the optical properties of the record carrier at the test marks change when the record carrier is irradiated at the maximum erase power at the test marks, such that the normalized reflected power becomes maximal;
- means for determining the optimal modifying power (PM) from the equation P M = χ · ( P min + P max ) α
- in which α is a constant known in advance and χ is a variable which is dependent on properties of the record carrier.
Dependencies are inferred from the claim text.